Process of separating and purifying wax-containing materials



Patented Sept. 21, 1937 PAT, r OFFICE;

25093538 rnooass or SEPARATING AND PURIFYING WAX-CONTAINING MATERIALS Harry ll. Bennett and Dwight E. Manes;"I lll'sa, Okla, assignors. to Mid-Continent Petroleum Corporation, Tulsa, Okla, acorporation of Delaware Na -Drawing.- Application March 15," 19

Serial N0. 11,248

5 drocarbon oils, and also in the separation of different waxes.

Prior to this invention, hydrocarbon oils have been usually dewaxed by diluting the oil with a solvent, or diluent, chilling the resultant solution to a very low temperature, and thereafter removing the precipitated wax.

Various solvents, or diluents, have been proposed to expedite the removal of the wax. These old solvents have not been entirely satisfactory as they usually had a relatively high solvent action for the wax as well as the oil, and have, therefore, provided an inefiicient means for the separation of the wax from the oil. 1

A mixture of two solvents, one with a comparatively high solvent power for the oil and wax, and the other with a relatively low solvent power for wax, has also been proposed.

A dewaxing process wherein 'a'mixture of such solvents is employed usually requires a temperature of F., or lower, to obtain a complete removal of the wax. Other difiiculties in these old processes include changes in the ratio of the constituents of the diluent when the dewaxing operation is carried out in two or more stages.

We have discovered a solvent, which may be employed alone or in combination with other solvents, which has a very low solvent power for wax and an exceptionally high solvent power for oil so that Wax may be readily precipitated from the oil with no tendency to throw the oil out of solution.

We have found that octyl alcohol has an unusually high solvent power for oil with a comparatively low solvent action for wax. Octyl alcohol has these very desirable properties to an entirely unexpected degree. Some of the otheraliphatic alcohols have these properties to a limited extent, but they do not accomplish the desirable results obtained from octyl alcohol, and they are not adaptable for various stocks which can be very effectively dewaxed by the peculiar action of octyl alcohol.

While octyl alcohol can be very effectively used alone, or in combination with other alcohols, to

action: toward the wax without causing any oil to be thrown out of solution even at very low temperatures. The use of acetone, or the like, with octyl alcohol also additionally reduces the viscosity of the solution and facilitates the precipitation of wax in a form that filters readily.

Acetone has a low solvent action for both wax and oil, but in combination with octyl alcohol, its solvent action for oil is such that oil is not thrown out of solution until the wax is com- 10 pletely precipitated.

Another advantage of octyl alcohol lies in the fact that it permits use of a relatively large percentage of acetone, or the like. If too much acetone is used, the oil may be thrown out of solutio-n. It is important tostay below the concentration of acetone, which will bring this about. This varies from 40% to 60% acetone at dewaxing temperatures. The quantity of acetone may be as high as approximately 60% of the combined acetone and octyl alcohol.

In carrying out our process, the Wax may be removed from the oil in one or more stages, and 5 when wax of different melting points is desired, we prefer to remove the wax in two or more stages at different temperatures.

Due to the exceptionally high solvent action of our solvent for oil and very low solvent action for wax, the filter cake, if the wax is separated from the oil by filtering, may be very effectively washed with some of the solvent to remove any oil and provide a clean white wax.

The proportions of the octyl alcohol may be varied as desired in accordance with the material to be treated, or to obtain specific results desired by the operator, and it is to be understood that the invention is not limited to such details. However, as a specific illustration of one form of the invention, we will describe the treatment of a petroleum distillate having a Saybolt universal viscosity of 65 at 210 F., and a cold test of 86 F.

One hundred gallons of said petroleum distillate may be dissolved in fifty gallons of octyl alcohol (Z-ethyl hexanol) at a temperature of about 100 F., or higher. Fifty gallons of acetone may then be added to the solution and the resultant solution cooled to 70 F., at which temperature 40 to 50 percent of the Wax present is precipitated. The solution is then filtered to remove the precipitated wax, and the filter cake may be washed with one hundred gallons of an equal mixture of octyl alcohol and acetone. The filter wash may be mixed with the filtered solution to further dilute it.

The more dilute solution may then be chilled to 10 to 15 F., and again filtered to remove an additional quantity of wax. This filter cake may likewise be washed with a mixture of octyl alcohol and acetone to recover as much oil as possible and purify the wax.

The dewaxed solution is then distilled to remove the solvent. The resultant dewaxed oil will have a cold test of -10 F. The higher melting point wax is crystalline in character, and it melted at 150 F. The wax obtained at the lower temperature melted at 122 F.

While we have described the treatment of a lubricating oil stock to remove wax, it is evident that our invention may be employed to separate and purify waxes of any desired melting point from petroleum mixtures, such as wax distillate, slack wax, petrolatum, etc.

We claim:

1. The process of dewaxing hydrocarbon oils which comprises dissolving a wax-containing oil in 2-ethyl hexanol, precipitating wax from the solution, and removing the precipitated wax.

2. The process of dewaxing hydrocarbon oils which comprises dissolving the wax-containing oil in 2-ethyl hexanol and another solvent having a relatively low solvent action for the wax, cooling the resultant solution to precipitate wax, and separating the precipitated wax from the solution.

3. The process of dewaxing hydrocarbon oils which comprises dissolving the wax-containing oil in Z-ethyl hexanol and acetone, cooling the resultant solution to precipitate wax, and separating the precipitated wax from the solution.

4. The process of separating wax from wax mixtures, which comprises dissolving the wax mixture in 2-ethyl hexanol, cooling the resultant solution to precipitate wax, and removing the precipitated wax from said solution.

HARRY T. BENNETT. DWIGHT B. MAPES. 

